In general, a rocker (side sill), which extends in a longitudinal direction and has a hollow closed cross-section, is provided at a lower portion of a vehicle body, and both side portions of a floor panel, a lower portion of a center pillar, and the like are connected to the rocker. As a vehicle body side structure that includes this kind of rocker, a structure where both ends of a floor panel are curved upward along the side surface of a rocker so as to form flanges and the flanges are bonded to the side surface of the rocker is disclosed in, for example, Patent Literature 1.